First, let's define the two words from Dictionary.com.
Affect is usually a verb, meaning:
- To act on; produce an effect or change in: Cold weather affected the crops.
- To impress the mind or move the feelings of: The music affected him deeply.
- To attack or infect, as a disease: Rheumatic fever can affect the heart.
Effect is usually a noun, meaning:
- Something that is produced by an agency or cause; result; consequence: Exposure to the sun had the effect of toughening his skin.
- The power to produce results; efficacy; force; validity; influence: His protest had no effect.
- A scientific law, hypothesis, or phenomenon: the photovoltaic effect.
- Advantage; avail: used her words to great effect in influencing the jury.
- The condition of being in full force or execution: a new regulation that goes into effect tomorrow.
- Something that produces a specific impression or supports a general design or intention: The lighting effects emphasized the harsh atmosphere of the drama.
- A particular impression: large windows that gave an effect of spaciousness.
- Production of a desired impression: spent lavishly on dinner just for effect.
Even with the definitions, sometimes it's hard to pick. Here are a few rules:
1. Use "affect" as a verb when you're talking about influence.
- Eating too many bon bons can affect your weight.
- Running into a werewolf was really affecting her mood.
2. Use the "effect" if you're talking about results or to describe something that was caused or brought about.
- The effect of eating an entire pound of bon bons was immediate and uncomfortable.
- I cannot effect change in my life without a huge bundle of cash.
3. Use "effect" whenever it is preceded by any of these words: a/an, and, any, into, no, the, take(n) (with or without an adverb).
- Meeting a unicorn always had a calming effect on her.
- The magic wand had an effect on the frog.
- It's all about cause and effect.
- The werewolf had no effect on her mood at all.
- The effect of the vampire bite was instantaneous.
Here is a quiz. See if you can get them all right.